The soul descends to elevate the body

במד' אחור וקדם צרתני זכה אדם נוחל ב' עולמות וא"ל בא ליתן דין וחשבון.

In the Midrash: "Back and front You have formed me" (Tehillim 139:5) — if a person is worthy, he inherits two worlds; and if not, he comes to give a reckoning (din v'cheshbon).

The Midrash reads "back and front" as the two possible outcomes of the dual nature of man: a worthy person inherits both worlds, while an unworthy one must give an accounting.

כי האדם כלול מעליונים ותחתונים.

For man is composed of the upper and the lower realms.

The human being is a unique blend of the heavenly (his soul) and the earthly (his body).

חומר וצורה.

Matter and form.

He is both physical matter (the body) and spiritual form (the soul).

והנה הנשמה שיורדת בגוף הוא לתקן גם הגוף כדרך הצדיקים שמהפכין את החומר לצורה וממשיכין הארת הנשמה לגוף.

And behold, the neshamah that descends into the body comes to rectify the body as well, in the way of tzaddikim who transform matter into form and draw the illumination of the neshamah into the body.

The soul's descent has a purpose: to elevate the body too. Tzaddikim convert the physical into the spiritual, drawing the soul's light into their very flesh.

וזה נוחל ב' עולמות.

And this is "inheriting two worlds."

One who elevates his body along with his soul thereby gains both this world and the next.

והרשעים להיפוך בחייהם קרוין מתים.

And the resha'im (wicked) are the opposite — in their lifetimes they are called dead.

The wicked do the reverse, dragging the spiritual down into the physical, and so they are considered "dead" even while alive.

כי הצורה נהפך לחומר.

For the form is turned into matter.

Instead of elevating matter into form, they coarsen their spiritual form into mere matter.

ומגשמים גם את הנשמה.

And they make even the neshamah physical.

Their conduct drags down even the lofty neshamah into materiality.

וע"ז יש דין על איבוד ופגם שעשו בנשמה.

And for this there is judgment (din) — for the destruction and blemish they caused to the neshamah.

The "judgment" is for the active damage they inflicted upon their own soul.

וחשבון על שלא הרויחה הנשמה בירידתה בגוף.

And reckoning (cheshbon) — for the fact that the neshamah did not gain anything from its descent into the body.

The "reckoning" is for the lost opportunity: the soul came down to gain, and the wicked person wasted that mission.

והקב"ה נתן לנו ע"ז תרי"ג מצות.

And the Holy One, blessed is He, gave us for this the 613 mitzvos.

To accomplish the soul's purpose of elevating the body, Hashem gave the 613 mitzvos.

רמ"ח מ"ע להאיר כח הנשמה בגוף ע"י המ"ע כמ"ש וחי בהם.

The 248 positive commandments — to illuminate the power of the neshamah within the body through the positive mitzvos, as it says, "and live by them" (Vayikra 18:5).

The positive mitzvos, corresponding to the 248 limbs, draw the soul's light into the body, infusing it with life.

והמל"ת הם לשמור הגוף וחומר שלא יעשו פגם בנשמה.

And the prohibitions are to guard the body and the matter, so that they should not cause a blemish in the neshamah.

The negative commandments protect the soul by restraining the body from actions that would damage it.

כי בכל המעשים אשר אסרה התורה הם דברים שא"י להמשיך אותם אל הקדושה והרוחניות.

For all the actions that the Torah forbade are things that cannot be drawn into kedushah and spirituality.

The Torah forbids precisely those acts that are incapable of being elevated and channeled toward holiness.

לכן ענין מל"ת נגד שס"ה גידים שלא יסתמו דרך הילוך החיות וכח הנשמה.

Therefore the matter of the prohibitions corresponds to the 365 sinews, so that they should not block the pathway of the flow of life and the power of the neshamah.

The 365 prohibitions correspond to the 365 sinews; like clear channels, they keep the conduits of spiritual life-force from becoming clogged.

וב' הנ"ל הם בחי' זכור ושמור.

And these two are the aspects of "Remember" (Zachor) and "Guard" (Shamor).

The positive mitzvos parallel "Zachor" and the prohibitions parallel "Shamor" — the two formulations of the Shabbos command.

וכל זה תלוי בזיכוך הגוף כמ"ש זכה נוחל.

And all of this depends on the refinement (zikuch) of the body, as it says, "if he is worthy (zacha), he inherits."

Everything hinges on purifying the body — being "zacha" (worthy/refined) is what enables one to inherit both worlds.

וע"ז אז"ל רצה הקב"ה לזכות את ישראל כו' הרבה להם תורה ומצות.

And about this Chazal said: the Holy One, blessed is He, wished to give merit to (l'zakos) Yisrael, therefore He gave them abundant Torah and mitzvos (Makkos 23b).

The very purpose of the abundance of mitzvos is "l'zakos" — to refine and grant merit to Yisrael, the same root as "zacha."

ושבת הוא זכור ושמור כלל כל המצות.

And Shabbos is "Remember and Guard," the inclusive principle of all the mitzvos.

Shabbos, with its dual "Zachor" and "Shamor," encompasses the entire body of positive and negative mitzvos.

והוא בחי' אחור וקדם.

And it is the aspect of "back and front."

Shabbos itself embodies the "back and front" duality of the opening verse — uniting both dimensions.

שהשבת הוא מעין עוה"ב.

For Shabbos is a taste of the World to Come.

Shabbos is the "front"/future aspect — a foretaste of Olam Haba.

והקדושה יורדת בו לעוה"ז לבנ"י כמ"ש בזוה"ק פ' ויקהל מענין זה.

And the kedushah descends on it into this world to Bnei Yisrael, as written in the Zohar HaKadosh, Parshas Vayakhel, regarding this matter.

On Shabbos the holiness of the upper world comes down into this world for Yisrael — the meeting of "back and front."

לכן אומרים בקידוש ושבת קדשו כו' הנחילנו לשון נסתר רומז על שבת עליון.

Therefore we say in Kiddush, "and His holy Shabbos... He gave us as an inheritance," in the hidden (third-person) form, alluding to the upper Shabbos.

The third-person "His holy Shabbos... He gave us" points to the transcendent, "upper" Shabbos.

ושבת קדשך כו' הנחלתנו רומז על שבת תחתון.

And "Your holy Shabbos... You gave us as an inheritance" alludes to the lower Shabbos.

The second-person "Your holy Shabbos... You gave us" points to the immanent, "lower" Shabbos that descends into this world.

והם ב' נחלות שבמדרש.

And these are the two inheritances of the Midrash.

These two Shabbos formulations are the "two worlds/inheritances" the Midrash spoke of.

נוחל ב' עולמות.

"He inherits two worlds."

The pair of Shabbos inheritances embodies the Midrash's promise that the worthy person inherits two worlds.

שבשבת מזדככין נפשות בנ"י ונוחלין ב' עולמות:

For on Shabbos the souls of Bnei Yisrael are refined, and they inherit two worlds.

Shabbos is the time when Yisrael's souls are purified (zikuch), enabling them — like the worthy person of the Midrash — to inherit both this world and the next.

Summary: Man is a blend of upper and lower — matter and form, body and soul. The soul descends in order to elevate the body, transforming matter into form as the tzaddikim do; one who does so "inherits two worlds," while the wicked, who drag the spiritual down into the physical, are "called dead" and face judgment and reckoning. The 613 mitzvos serve this purpose: the 248 positive mitzvos draw the soul's light into the body's limbs, and the 365 prohibitions keep the soul's channels (sinews) unblocked — paralleling Zachor and Shamor. Everything depends on refining the body, and Shabbos, which unites both "Remember and Guard," is the time when Yisrael's souls are refined and they inherit both worlds — reflected in the two inheritances of "His holy Shabbos" and "Your holy Shabbos."